NEW YORK (Reuters Health) – A commercially available formula of Lactobacillus acidophilus and L. casei prevents Clostridium difficile infection and diarrhea during antibiotic treatment, according to a single-center study from China.

Although meta-analyses indicate that probiotics decrease antibiotic-associated diarrhea, most trials are flawed, senior author Dr. Larry E. Miller and colleagues state. They say that their randomized, double-blind trial is the largest to address these issues and the first to examine dose effects.

The trial included 255 hospital patients, ages 50 to 70, receiving penicillin, cephalosporin or clindamycin. Within 36 hours of starting antibiotic therapy, patients began to take (each day, 2 hours after breakfast) either 2 probiotic capsules (n = 86), 1 probiotic capsule and 1 placebo capsule (n = 85), or 2 placebo capsules (n = 84). All patients were hospitalized for at least 5 days and received antibiotics for at least 3 days (but not more than 14 days). They continued with their assigned treatment for 5 days after finishing the course of antibiotics.

Each probiotic capsule contained 50 billion colony-forming units of L acidophilus CL1285 and L. casei.

As reported online February 9 in the American Journal of Gastroenterology, at 21 days after the end of their assigned treatments, the incidence of antibiotic-associated diarrhea was 44.1% in the placebo group, 28.2% in the 1-capsule group and 15.5% in the 2-capsule group.

Rates of diarrhea due to C. difficile were 23.8%, 9.4%, and 1.2% with placebo, 1 capsule, and 2 capsules, respectively.

The authors estimate that treating five patients at the higher probiotic dose would prevent one case of C. difficile-associated diarrhea.

Overall, the 2-capsule group had the lowest rate of gastrointestinal symptoms, followed by the 1-capsule group. The investigators observed a similar pattern for symptom duration.

They attribute their high response rates to the high probiotic dosage: